In defence of the classroom science demonstration

Science demonstrations are often criticised for their passive nature, their gratuitous exploitation, and their limited ability to develop scientific knowledge and understanding. This article is intended to present a robust defence of the use of demonstrations in the classroom by identifying some of their unique and powerful benefits – practical, affective and cognitive.

The science demonstration is thriving in informal science education. Demonstrations feature strongly in popular science television programmes; science demo theatre productions have toured the UK; Steve Spangler’s demonstrations have been awarded their own You Tube original content channel. Demonstrations are even seeping into popular culture. Over 100 million people have watched the explosive and beautiful results of two performers dropping 500 Mentos mints into 100 bottles of diet coke in the world’s first viral demo. In the classroom, however, the science demonstration appears to be under threat.

Opening arguments for the prosecution

Classroom demonstration: a pathetic and ingenious form of minor physics in which the stage setting counts for more than concept. It is neither illusionism nor conjuring trick but borders on them. Primo Levi (chemist and writer)

Some of the most common criticisms and challenges facing classroom science demonstrations include:
• lack of time or equipment;
• fears that the demonstration may not work;
• concerns about the perceived safety of more spectacular demonstrations in an increasingly litigious environment;
• accusations that “whizz bang” demonstrations give a misleading and damaging impression of what scientists really do;
• pervasive belief that passively watching a demonstration is less effective than conducting a hands-on practical experiment;
and most crucially,
• concerns about the lack of evidence of what students actually learn from demonstrations.

The case for the defence

There are three main threads to this argument defending science demonstrations in the classroom – the logistical case; the affective case (emotions and attitudes); and the cognitive case (knowledge, understanding and skills).

The mundane logistical case

The normal justifications given for demonstrations are that, in many cases, they are cheaper, quicker, easier, safer and less disruptive than having each pupil do the related practical investigation. Whilst these logistical benefits are undeniably true in certain cases, and cannot be discounted in the pressurised reality of the classroom, I find them the least convincing reasons for performing class demonstrations. They come from the widespread philosophy which, explicitly or implicitly, believes demonstrations are easier-to-organise poor substitutes for hands-on practical activities. I believe that this hasty assumption, however, does a great disservice to the true power of classroom demonstrations.

The easy affective case

Demonstrations can be emotionally engaging science theatre. This assertion is not meant be to pejorative in any way. Theatres are laboratories of human emotion and interest management. Stella Alder (2000, 107), the renowned acting coach, once famously declared,

On stage you cannot afford to be boring, even for one instant.

Now obviously classrooms are not stages. In every lesson students allow teachers to be boring – without walking out. Their physical attendance, of course, says little about their mental presence. Students who are strongly self-motivated in science can sustain their attention through these moments of boredom. Many students, however, cannot delay their gratification in this way – without emotionally engaging them first to secure their attention, no cognitive outcomes can possibly follow.

Capturing and holding interest

The novelty, spectacle and inherent drama of a classroom demonstration can provoke significant interest from students. Psychologists call this kind of interest, situational interest – it arises from the content or presentation method and spontaneously creates interest for almost all students. It can be extremely powerful while it lasts, but it tends to be short-lived. How this situational interest can progress to a more enduring, but personal, form of interest – individual interest – is the holy grail of interest research.

The almost universal nature of situational interest, however, can create exceptionally powerful and intense moments of complete focus from a class watching a demonstration. This group dynamic stems from social facilitation, a form of “social proof”, where we tend to take our lead from the attention given to a situation by those around us. So, if most of the students are intently watching, the less engaged students instinctively feel that it must be important and they mimic their peers; there is pin-drop silence.

Some critics dismiss students watching a teacher demonstration as passive. It appears that the dominant theory of constructivism has been unfairly conflated by some with hands-on and “active learning” methodologies. We construct meaning from all of our experiences, not just those in which we are physically active. In fact, I would argue that the level of concentrated group attention attained with effective demonstrations is difficult to achieve through most other classroom activities.

Other detractors condemn the gratuitous use of spectacular demonstrations as a disingenuous way to motivate students to study science. If the emotional engagement derives from a showmanship device which is external to the science, then I would agree that such external hooks need to be used very judiciously to avoid giving the damaging impression that we need “to make science fun” (McCrory, 2011). If, however, the engagement arises from hooks which are inherent to science so that you are merely “letting the fun inside science out” (e.g. explosions; colour changes; the suspenseful delay until a chemical reaction occurs) then I find this criticism harsh. Are teachers to ignore some of the most viscerally appealing aspects of science, simply because they do not represent all that there is to a career in science? It is fair to say, though, that such demonstrations could often be better framed in a broader context which celebrates some of the other, more intellectual, rewards of understanding science.

Exploiting the primitive power of curiosity

Curiosity is the emotional itch that, try as you might, you simply cannot avoid scratching.
Scientists are frequently driven by a powerful curiosity about the world, and being curious is a scientific attribute to be valued in its own right. In today’s assessment-driven classrooms, Ian Russell’s aphorism reminds us the value of longer-term outcomes (Russell, weblink):

Give people facts and you feed their minds for an hour.
Awaken curiosity and they feed their own minds for a lifetime.

Demonstrations are perfectly suited to exploiting curiosity, the powerful engine driving most of our learning. The “information gap theory” of curiosity proposes that people do not like to know that they do not know something (Lowenstein, 1994). When a demo creates, or makes students aware of, a small gap in their knowledge of the world, they will be compelled to try to fill that gap.

If you tell students what is going to happen before you perform the demonstration or explain the outcome too soon, you relinquish the most potent appeal of any demo. If you state learning intentions at the wrong time, it serves as a spoiler for the suspense to follow. As Lawrence Bragg, who founded the schools lecture programme at the Royal Institution, observed in his advice to lecturers,

How dull a detective story would be if the writer told you who did it in the first chapter and then gave you the clues.

This counsel may sound obvious, but this is probably the most common trap which teachers fall into when they demonstrate. It is often driven by a pedagogy which is dominated by a need to explain concepts quickly rather than being able to invest time to explore the phenomena first. Be patient and tease your students with clues. Curiosity does inevitably require time to nurture, so it is up to your professional judgement to balance this need against other learning outcomes. It is also vital to monitor your students carefully, so that curiosity does not tip over into frustration.

An important, but neglected, source of suspense inherent in any live demonstration derives from milking the simple tension – “Will it work?” As you know, when demonstrations don’t work, this can be even more engaging for students. The demo failure breaks the predictable pattern of most activities “working” in class; they savour seeing an authority figure momentarily foiled; and they think they are getting to see a unique live event that no other class has witnessed before. Like watching their hero in a film struggle as the challenges ratchet up, they hope that your true character will emerge under this stress; and are fascinated to see how you will cope. So despite how vulnerable demonstration failures may make you feel, they should be enthusiastically embraced, rather than feared. (BOX 1)

Demonstrations which result in injury are, of course, a different matter. However, provided an adequate risk assessment has been carried out and the control measures followed, there are actually very few demonstrations which are banned either nationally or at a local authority level.

BOX 1 When demonstrations go wrong …
The fear of a demonstration failing in public is usually more of a problem which affects your confidence than one which impacts negatively on the students. It is only when you have a series of failures that your credibility and that of your subject begins to suffer.

Tips for coping with demo failures:
• Practise thoroughly to reduce the likelihood of a failure. When they do fail, as they inevitably will at some point, embrace this opportunity to improvise and to take advantage of the suddenly increased focus from your students.
• Keep calm and fake your confidence. If you do not show undue concern or embarrassment, neither will your students.
• Model the scientific method as you analyse with the students what may have gone wrong and try to fix it.
• Learn from the experience so that you can either avoid the problem or incorporate it into your teaching as a planned failure.

Sharing your passion

Students, like theatre audiences, enjoy shared emotional experiences. Demonstrations can emotionally engage your students and reveal your passion for your subject. Your students will feel what you feel, or at least what feelings you model – curiosity; anticipation; uncertainty; confusion; surprise; intellectual joy of understanding; wonder; sense of imagination; amusement; sense of beauty; fear; or amazement. This is known as emotional contagion, and you can exploit this basic human facility by using your feelings as an “emotional backing track” to the demonstration to cue them how to react. Being able to perform the same demonstrations, time after time, and still express these emotions convincingly is a vital but challenging teaching skill. In the theatre they call this modelling of emotions creating the “illusion of the first time”.

Have you ever noticed how bringing up a class around a demonstration generates strong reactions? The more densely-packed your students and the more easily they can see each other’s faces, the faster their emotions will spread. The most emotionally expressive students will innocently infect the students next to them, like “emotional beacons”. In fact, any volunteers you use in a demonstration, because they represent the class, will be even more emotionally contagious than you.

By exposing your genuine enthusiasm for science through demonstrations, you are undeniably making yourself vulnerable to mockery. It is precisely the risk and truthfulness inherent in this self-disclosure, however, which makes your performance so watchable to your students. This strategy can also help to develop better relationships with your students.

The affective benefits of demonstrations are, I believe, valuable outcomes in their own right. The strong psychological effects of novelty, social proof, curiosity, emotional contagion, modelling emotions and self-disclosure can create moments of unique communal emotion and focus amongst your students. Their additional value, however, lies in generating fertile conditions for cognitive learning.

The tricky cognitive case

There’s an elephant in the room when it comes to teaching science. I would respectfully suggest that students learn much less from any particular lesson than we would like to accept. The non-intuitive and abstract nature of most scientific principles, combined with the stubborn resistance of our brains to abandon our misconceptions makes cognitive learning from a single exposure to any teaching strategy highly unlikely. This applies equally to demonstrations as it does to any other technique.

From a constructivist perspective, teaching is like patiently feeding coins into shove penny machines. Often frustrating, and occasionally exhilarating. Nudge. Nudge. Nudge. Learning is a gradual, cumulative, messy process. You never know which nudge is eventually going to cause the figurative pennies to drop as the evidence slowly mounts against the misconception in the mind of the student. As educators, our egos live for the thrilling, noisy cascades of coins. But we should no more claim these victories as exclusively our own, than we should feel disheartened when our carefully-thought-out demonstration merely contributes another silent nudge. It is the patient and repeated exposure of ideas to learners over time and from many different sources (formal, informal and everyday life) which makes learning possible.

The most comprehensive literature review of 90 years of demonstration impact studies (Majerich and Schmuckler, 2008, p 13) poses an awkward, but central, question to advocates of science demonstrations – why do so many teachers anecdotally report benefits to demonstrations when the research evidence for positive student outcomes is “rather dismal”? They suggest two possible explanations – the studies almost always naively attempted to measure outcomes from single exposures to a demonstration; and generally the research took little account of how the demonstration was integrated with the rest of the students’ experiences.

To these serious shortcomings, I would add the criticism that the research studies did not properly investigate the affective outcomes of demonstrations and how these outcomes may have stimulated cognitive gains. Furthermore, informal science educators who specialise in performing demonstrations will often assert that the true art of demonstration lies in the detailed execution of the techniques used to present the demonstration, rather than in the demonstration itself e.g. maximising sight lines and choreographing your movements; audience interaction throughout the demonstration; demonstration plot; curiosity, uncertainty, anticipation and surprise techniques; emotional modelling; self-disclosure; volunteers; improvisation; storytelling; and use of humour. I would argue strongly that demonstration impact studies need to take more account of these techniques as significant variables if they are to draw any credible, generalisable conclusions about the cognitive effectiveness of demonstrations.

Critics of science demonstrations frequently forget that demonstrations are typically a starting point in the educational journey, rarely a destination. Despite the above challenges inherent in developing knowledge and understanding, I believe there are specific benefits afforded by demonstrations which are, directly or indirectly, relevant to these cognitive outcomes.

Showing authentic, concrete and memorable phenomena

Demonstrations should transparently and convincingly show authentic phenomena (Figure 2). The value of this cannot be understated. The Royal Society’s motto encapsulates one of the corner-stones of how science works, “Nullius in verba” – loosely translated as “take nobody’s word for it”. Demonstrations can help students to observe phenomena with their own eyes. Sadly, however, it is not always straightforward to let them observe precisely what you want them to see (Figure 2).

BOX 2 The difficulty of pointing things out

Curiously, “teach” and “demonstrate” share the same original meaning – to point out (from the Old English “tæcan” and the Latin “monstrare” respectively). In fact, the original meaning of “teacher” was the index finger we use for pointing. In this sense, it could be argued that all teachers are demonstrators who point things out.
Pointing things out, however, is fraught with difficultly. Simply exposing students to an authentic phenomenon is normally not enough for them to appreciate what they are actually observing, for several reasons. Firstly, it may seem obvious to you where to focus your attention. You are cursed by your knowledge from having performed the demonstrations many times. To the uninitiated eyes of a student, however, it is sometimes not clear which elements are the most salient ones. Secondly, even if they are looking at the right place at the right time, their highly selective attention is biased by their misconceptions. This can cause them to unconsciously ignore what actually happened in order to preserve their misconceptions and self-esteem. Even more frighteningly, students can witness a demonstration, intended to disprove their misconception, and yet perceive the outcome in such a way that it supports their misconception. It seems there are few ends to which our cunning brains will not resort in order to protect our view of the world.
Faced with such stubbornness, it is essential to be explicitly clear where you want your students’ attention when watching demonstrations and to help them identify what changes might be significant. This is one advantage of demonstrations over student practical work, where you have much less control over what students are focussing on. For demonstrations with a surprising reveal, this cueing is often better done when you repeat the effect.

The power of demonstrations to “show, rather than tell” has probably been no more publicly validated than Richard Feynman’s famous demonstration showing the effects of cold temperatures on O-ring flexibility at the Challenger Space Shuttle commission. This disarmingly simple piece of television science theatre made the phenomenon concrete and observable for everyone (Feynman, weblink).

At best, well-executed demonstrations show scientific phenomena. It is essential to remember that, by themselves, demonstrations do not tend to reveal the fundamental principles underlying the phenomena. Demonstrations can give examples of these principles in action, but to discern the abstract, general principle from the concrete, specific phenomenon usually requires one of three conditions – prior understanding from the student; carefully scaffolded interpretation from the teacher; or scientific genius.

Can you remember a demonstration you saw as a student? Students often have vivid memories of demos they have witnessed. In one study, Abrahams and Millar (2008) found that the emotional intensity of the activity was more important in determining student recall than whether the student had simply watched the demo or physically taken part in the practical activity. Given this memorability, demonstrations of phenomena therefore have value solely in enriching the library of experiences of your students. In the future, students may connect these experiences with principles they are being taught. Learning is a messy, non-linear process.

Provoking interaction, thought and discussion

The act of demonstrating can, in itself, help to stimulate more natural interactions between you and your students. Their prompted responses and completely spontaneous comments provide a golden opportunity for you to connect with them and with their unedited ideas. Older students can become so engaged in the demonstration that they forget to edit their verbalisations through their normal teenage filter of calculated indifference.

Many demonstrations are based on surprising or counter-intuitive outcomes which provoke thought from students as they try to align the result with their expectation. This cognitive conflict strategy requires careful management so that the conflict between the outcome and their misconceptions is made explicit, and so that the conflict is not perceived to be so large that students either completely dismiss or distort the outcome (BOX 2).

Counter-intuitive outcomes can generate lively discussions amongst the class. Two of the variables most often studied in demonstration impact research are the effect of:
• requiring students to make and discuss public predictions of the outcome, and
• giving students significant time after the demonstration to share their possible explanations.
Encouraging students to publicly predict the outcome greatly increases the suspense and emotional jeopardy of any demonstration – not only are they curious about what will happen; they now intensely care if their own public prediction will be correct. A wide range of studies has found these structured discussion strategies increase the cognitive gains achieved (Zimrot and Ashkenazi, 2007). This research has led to the uptake of demonstration teaching models based on the following sequence: PREDICT – OBSERVE – DISCUSS – EXPLAIN

Developing scientific thinking skills

In addition to showing how important the under-valued skill of observation is in science, demonstrations can also allow you to exemplify scientific thinking and models of scientific method. The high degree of control that you have when delivering a demonstration allows you to talk aloud your thoughts and ask questions as you explicitly work through the various stages and problems of an “experiment”. It is perhaps more realistic to deconstruct these complex skills through a demonstration, than it is to expect students to somehow distil them when they are caught up in the hands-on excitement and distraction of making their own pseudo-experiments “work”.

The clinching argument

I have a confession to make. The separation of the defence of demonstrations into affective and cognitive arguments is artificial and close to meaningless. It is impossible to separate cognition and affect in the brain – they are inextricably bound up together in a beautiful way we don’t truly understand yet (Damasio, 2006). So even if you work in an environment where you can only afford to care about the measurable cognitive results of each classroom activity, the strong, emerging consensus of recent neuroscience research would suggest it is impossible to separate these outcomes from the affective domain. The stark, uncomfortable implication of this research is that if you ignore this affective aspect of your teaching, you will inevitably damage the potential cognitive outcomes your students can achieve.

Summing up for the defence

Demonstrations are tools. Like any tool, they have strengths and limitations, and you need to understand these factors in order to use the tool effectively with your students. This article is absolutely not arguing against using hands-on experiences, but it is rather an attempt to identify the value that demonstrations can have alongside class practical work and the other techniques in your teaching toolkit.

Demonstrations can be emotionally engaging science theatre. Their unique power lies, like theatre, in their impact on the communal emotional engagement and focus of your students. Like theatre, demonstrations have enormous potential to – create and sustain interest; stimulate curiosity; communicate and share emotions; reveal phenomena by showing, not just telling; direct focus; and to provoke further interaction, thought and discussion.

We should stop thinking of demonstrations solely in terms of their direct impact on cognitive outcomes. If only learning was that simple and quick. The fixation with trying to measure what students learn cognitively from demonstrations confuses the destination with the journey. Demonstrations are much more about slowly nudging students along an absorbing educational journey, rather than trying to rush them to the destination and losing them along the way.